Catch-up of delayed tooth eruption associated with uranium intoxication.

The population at large is at risk of oral exposure to uranium. Previous studies performed at our laboratory showed delayed tooth eruption 7 d post-administration of a single oral dose of uranyl nitrate in newborn rats. Rat kidney exhibiting severe damage 2 d post-acute uranyl nitrate exposure showed signs of recovery after 7 d; however, tooth eruption and development were significantly lower as compared with their age-matched controls. The aim of the present work was to establish whether tooth eruption and development, delayed by uranium exposure, can catch up to normal values at longer experimental times. In addition, since it is well documented that uranium intoxication by other routes of entry causes alterations in bone growth, we also aimed to evaluate the effect of oral exposure to uranium on mandibular growth. An experimental group of 16 1-d-old Wistar rats received a single 90 mg kg-1 body weight oral dose of uranyl nitrate. Another group of 16 age-matched rats received an equal volume of saline solution and served as the control. Eight animals in each group were killed 7 d post-treatment, and the remaining animals were killed 27 d after the onset of the experiment. Morphometric measurements of mandibular growth were performed on radiographs. Tooth eruption and development were evaluated histomorphometrically on histologic sections obtained at the level of the mesial root of the first molar. Our results showed that the tooth eruption, dental development, and mandibular growth retardation observed 7 d post-acute uranyl nitrate exposure caught up completely after 27 d.

Exposure to oral uranyl nitrate delays tooth eruption and development.

The risk of oral exposure to uranium potentially involves the population at large. Tooth eruption and development are ongoing processes that begin during fetal development and continue until the age of 18 y. Since one of the mechanisms involved in tooth eruption is bone formation and it is well documented that uranium inhibits bone formation, the aim of the present work was to study the effect of oral administration of uranyl nitrate (UN) on tooth eruption and development. Wistar rats aged 1 and 7 d were orally administered a single dose of 90 mg kg(-1) body weight of uranyl nitrate. Two age matched groups received an equal volume of saline and served as controls. The animals were killed at 7 and 14 d of age, respectively. Mandibles were resected and processed to obtain bucco-lingual sections oriented at the level of the mesial root of the first mandibular molar, and histomorphometric studies were performed. Results showed that an acute high dose of uranyl nitrate delays both tooth eruption and development, probably due to its effect on target cells.